Muscle Tissue 武玉玲

Problems to solve 1.What are the general structures of skeletal muscle fiber? The general shape of skeletal muscle fiber is long cylindrical,1~40nm long, 10~100um in diameter. Each cell or fiber contains many nuclei,which are flat ovoid,peripheral placed beneath the sarcolemma.The sarcoplasm is acidophilic, containing a lot of myofibrils.

Each myolfibril is composed of alternating light and dark band. These bands arranged regularly, means dark band or light band always arranged in the same level, so the muscle fiber present cross striation.

2.What are the structures of muscle ? A piece of muscle is a organ which is formed by bundles of muscle fibers.Each muscle fiber is surrounded by thin layer of delicate supporting tissue named endomysium.The individual muscle cells are grouped together into elongated bundles called fasciculi.Each fascicle is surrounded by a thiker layer of loose collagenous tissue called perimysium.Many bundles of muscle fibers aggregate to form a piece of muscle surrounded by the thickest layer of dense collagenous sheath called the epimysium.Large blood vessels and nerves enter the epimysium and divide to ramify throughout the muscle in the perimysium and endomysium.

3.What is the difference between the cardiac muscle fiber and the skeletal muscle fiber under light microscope? The structure of cardiac muscle fibers are similar to those of the skeletal muscle fibers which are also striated muscle fibers,but in some way,they are different from skeletal muscle fibers. The following points show the differences between them: 1.The cardiac muscle cells are short cylindric, branched structures. 2.There is only one nucleus in the cardiac muscle fiber which located in the center of the cell. 3.The cross striations are less distinct than those of skeletal muscle fibers under light microscope because in cardiac muscle fibers,the myofilaments don ’ t Form a complete myofibrils. 4.The cardiac muscle fibers are joined together by a special structure know as the intercalated disc.

1.skeletal muscle a section of animal skeletal muscle, H&E stain Microscopic observation: There are 2 pieces of tissue on the slide,one of them is in longitudinal section, the other in cross section.

Low power: longitudinal section 1. skeletal muscle fiber 1

High power longitudinal section : 1.nuclei: ovoid,periphery located 2.cross striation: composed of alternating light and dark bands,which can be seen in this slide,but not very clear. 3.nucleus of supporting tissue 1 2 3

low power: cross section ： muscle fibers are round or polygonal in shape 1. skeletal muscle fiber 2. Perimysium 3. epimysium 2 3 1

High power: cross section of skeletal muscle fiber 1. skeletal muscle fiber 2. endomysium 1 2

High power: cross section of skeletal muscle fibers Each muscle fiber is round or polygonal in shape,which is surrounded by a layer of delicate supporting tissue.It is endomysium. The myofibrils are seen as fine dots.The nuclei are round in shape and located beneath the cell membrane. 1. muscle fiber 2. nucleus of muscle fiber 3. myofibril 4. endomysium

2. Longitudinal section of skeletal muscle fibers iron-hematoxylin stain In this section all structures are stained in black color and the cross striations can be seen very clearly.

21 3.cardiac muscle section of dog heart H&E stain

low power: this is longitudinal section of cardiac muscle fibers

High power: longitudinal section of cardiac muscle fibers which are elongated and branched structures.The cross striations can be seen also, but they are less distinct than those of skeletal muscle fibers. Each cell has only one nucleus which are ovoid and located centrally.Between 2 neighboring cells,we can find the step-like striation which is parallel to the cross striation called intercalated disc. 1. n ucleus of cardiac cell 2. intercalated disc. 3. cross striation 1 2 3

High power: cross section of cardiac muscle fibers They present round or polygonal in shape. some of them have around central nucleus, but some have no nucleus. Think of it,why? 1. cardiac muscle fiber 2. nucleus of cardiac cell 1 2

longitudinal section of cardiac muscle fibers iron-hematoxylin stain The cross striation and intercalated disk can be observed very clearly in this section.

4.longitudinal section of cardiac muscle fibers iron-hematoxylin stain high power: The cross striation and intercalated disk can be observed very clearly in this section. The intercalated disk is a limit line of 2 neighboring cells. It cross the muscle fiber, stained very dark.

5. smooth muscle cross section of dog duodenum H&E stain This is a hollow organ.Smooth muscle is situated in the peripheral red region of the organ. 29

Low power ： Smooth muscles are divided into 2 thick layers in peripheral part of the duodenum. The internal layer is longitudinal section. The external layer is cross section. 1. longitudinal section 2. cross section 1 2

High power: longitudinal section: The muscle fiber presents long spindle like shape,containing a centrally located oblong nucleus.The cytoplasm is acidophilic,has no cross striations.The fibers arranged in such a way that the thick middle portion of one cell lies next to the thin ends of neighboring cells. 1. Smooth muscle fiber 2. nucleus of muscle cell 2 1

High power: cross section of smooth muscle: They are appear a collection of rounded or ovoid structures. In some of which a central round nucleus can be seen. 1

High power: cross section of smooth muscle 1. smooth muscle cell 2.nucleus of muscle cell 1 2

Slide showing: 1.diagram of segment of skeletal muscle cell cut sarcolemma T tubule sarcoplasmic reticulum terminal cisternae triad myofibrils thin filaments thick filaments sarcomere

2.Diagram of segment of cardiac muscle fiber: 1)The T tubules are thicker and less frequent.In each sarcomere,there is only one T tubule which is located at the Z lines of each sarcomere. 2)The sarcoplasmic reticulum is not well developed as in skeletal muscle.They don’t form the terminal cisternae. So there are no triad, but diad.